The present invention relates to a code setting circuit and, more particularly, to a code setting circuit which has a conductive thin film fuse for trimming purposes.
With advancement in higher capability of and higher integration in integrated circuit devices in recent years, there has been a development of stronger desires for a higher accuracy in the setting of circuit conditions and lower power consumption. Especially for the setting of values of reference voltages or circuit currents in analog circuits, it is necessary to provide a circuit for adjusting a current value to a specified value by trimming methods since requirements to catalog specifications have been very strict. The trimming becomes fixed once the setting is effected in the course of a manufacturing process and cannot be readjusted at a later stage of the industrial application of a manufactured product. Such a circuit cannot have any changes in its permanent characteristics and should to be highly reliable without any fear of malfunction.
The conventional circuit for trimming purposes, that is, the trimming code setting circuit has problems in that the set trimming codes undergo changes with lapse of time during the service life of the circuit, and that since a steady-state current flows in the circuit, it is necessary to restrict the current to lower power consumption.